1. Field of the Invention
The present invention relates to tamper-evident containers and, more particularly, to a container having a closure which can be opened with a pull-tab attached to the closure along frangible lines, and tooling for manufacturing such a closure.
2. Description of Related Art
Retail containers for food or perishable items having tamper-evident closures or lids have been in regular usage for many years. In most cases, these containers are constructed for use with removable lids which positively seal the container closed during handling and shipping. The lids permit the purchaser to easily open the container, and then reapply the lid to reseal the container and store the remaining contents. For the consumer, evidence of tampering with the container or lid must be highly visible to quickly and reliably assess whether the contents have been potentially contaminated. The visibility of tampering is also important for the packager of the container from a marketing standpoint. For the manufacturer, the visibility of tampering is only one factor to consider, with the ease of manufacture also being a prime consideration.
Many prior art tamper-evident containers and lids are complex, relatively expensive to manufacture designs which employ lid locking structures and tear strips permitting removal of the lid locking structures in a way which make the tampering evident to the consumer. Existing designs employ either a tear-away or breakaway segment on the skirt of the lid, or on the container, which when removed allows access to the lid skirt for lifting the lid and opening the container. Tear-away lid skirt designs do not allow for effective liquid-tight reclosure, and are, in some instances, difficult to reapply and subsequently remove from the container.
Prior lids and containers are frequently formed from injection molded parts, which have complicated molded-in locks and tear strips formed by lines of weakness or frangible sections formed in the lids. Many lids are injection molded from a thermo-setting polymer, such as polyethylene. The lids are molded within a one-piece mold cavity and a one-piece mold core. The walls of the mold cavity form the external surface of the lid, and the walls of the mold core form the internal surface of the lid. Such a mold apparatus is shown in U.S. Pat. No. 4,691,501.
The capital expense required by the container manufacturer for production tooling is often prohibitively high. Moreover, because of the complex structure of the tamper evident locking apparatus, many lids include undercuts for which cam-action tooling must be mechanically activated before ejecting the lid from the mold halves. Such cam action tooling is more expensive than conventional static molds, and introduces production complications, such as timing and duration considerations, and the potential for breakdown.
Another manufacturing concern is that the tamper-evident feature not interfere with use of high speed spinning rod lid application machinery, such as that shown in U.S. Pat. No. 4,691,501.
Some prior tamper-evident container designs include projecting pull-tabs to remove the lid. These pull-tabs often extend outwardly and engage adjacent packages during shipment, so that vibration or other movement may accidentally cause partial removal or loosening of the lids. Additionally, the tamper evident tear strips are sometimes broken, falsely indicating that the container has been opened.
One container with a tamper-evident lid and pull-tab is shown in U.S. Pat. No. 4,627,550. The container includes an inwardly directed pull-tab which is connected to the upper surface of the lid with a plurality of frangible teeth which must be severed to utilize the pull-tab. Given the relatively hidden nature of the frangible teeth, the visibility of tampering is reduced. Indeed, it is conceivable that one could carefully sever the frangible teeth and gain access to the contents of the container, thereafter reattaching the pull-tab to the top surface of the lid without leaving much evidence of tampering. Additionally, the mold used to form the container lid must be relatively complex to release the lid after the frangible teeth are formed.
There is presently a need for an improved tamper-evident container and lid which is easy to manufacture and which includes a highly visible tamper-evident closure arrangement.